The present invention relates to an optical network system in which multiple types of low-speed signals are accommodated in an identical frame of a high-speed signal in a mixed manner and transmitted (including exchanged and forwarded), and more particularly, to an optical signal transmission technique which allows both of a SONET/SDH signal of about 10 Gbps and a 10 GbE-LANPHY signal whose bit rates are different from each other to be accommodated in a single 40-Gbps wavelength path in a mixed manner and transparently mapped.
In order to deal with an increased demand for data communications as represented by the Internet, larger-capacity communication systems are expected. As one of measures for larger capacity systems, increased-bit-rate communication systems have been studied. At this time, it is required to accommodate a conventional low-bit-rate signal in a frame of a high-speed signal whose bit rate is increased and transmit it.
For example, in Optical Transport Network (OTN) specified in ITU-T (International Telecommunications Union-Telecommunication Standardization Sector) Recommendations G.709, a frame format has been studied in which client signals of about 2.5 Gbps, such as Synchronous Optical Network (SONET) Optical Carrier-Level 48 (OC-48)/OC-48c signals or Synchronous Digital Hierarchy (SDH) Synchronous Transmission Module-Level 16 (STM-16) signals, are subjected to 16-channel multiplexing to generate an optical signal of Optical Transport Unit 3 (OTU3) for OTN having a transmission rate of about 43 Gbps.
Further, a frame format has been studied in which client signals of about 10 Gbps, such as SONET OC-192/OC-192c signals or SDH STM-64 signals, are subjected to 4-channel multiplexing to generate an optical signal of OTU3 for OTN having a transmission rate of about 43 Gbps.
Furthermore, a frame format has been studied in which 10 GbE-LANPHY signals (Ethernet™ signals) are subjected to 4-channel multiplexing to generate an optical signal corresponding to OTU3 for OTN having a transmission rate of about 44 Gbps.
In the above description, when a SONET/SDH signal and a 10 GbE-LANPHY signal which serve as client signals having a transmission rate of about 10 Gbps are taken up, the respective client signals can be accommodated by applying 4-channel multiplexing thereto, but since both the signals have different transmission rates, i.e., 9.95 Gbps and 10.3 Gbps, it is difficult to accommodate the signals in the same frame in a mixed manner.
With reference to FIG. 1 showing an example of a conventional optical network system, in a case where three 10 GbE-LANPHY signals (10.3 Gbps) and one SONET OC-192c signal (9.95 Gbps) are to be transparently mapped to a wavelength path of an OTU3 frame conforming to ITU-T Recommendations G.709, which has a bit rate of 40 Gbps for one wavelength, and transferred between nodes A and B constituting communication sites, for example, in New York and Boston, since the SONET OC-192c signal of about 10 Gbps and the 10 GbE-LANPHY signals have different bit rates, it is impossible to map both types of the signals to a single 40-Gbps wavelength path in a mixed manner.
Specifically, in the optical network system shown in FIG. 1, the transmission-side node A is configured by including, as transmission-side components, three layer 2/layer 3 switches (R) for transmitting the respective 10 GbE-LANPHY signals (client signals), a SONET/SDH Add/Drop Multiplexer (ADM) device for transmitting the SONET OC-192/OC-192c signal (client signal), an N-to-1 transponder (Muxponder) for multiplexing three client signals to generate an optical signal having a first wavelength and sending the optical signal to an optical multiplexer, a 1-to-1 transponder for sending one client signal to the optical multiplexer as an optical signal having a second wavelength, and the optical multiplexer for multiplexing (wavelength multiplexing) and sending the optical signal having the first wavelength received from the N-to-1 transponder and the optical signal having the second wavelength received from the 1-to-1 transponder to a single optical fiber serving as a transmission line.
The reception-side node B is configured by including, as reception-side components, an optical demultiplexer for demultiplexing (wavelength demultiplexing) and sending the optical signals having the first wavelength and the second wavelength received via the single optical fiber to an N-to-1 transponder and a 1-to-1 transponder, the N-to-1 transponder (Muxponder) for demultiplexing the optical signal having the first wavelength received from the optical demultiplexer to three client signals and sending them, the 1-to-1 transponder for sending the optical signal having the second wavelength received from the optical demultiplexer as one client signal, three layer 2/layer 3 switches (R) for receiving three 10 GbE-LANPHY signals from the N-to-1 transponder, respectively, and a SONET/SDH ADM device for receiving one SONET OC-192/OC-192c signal from the 1-to-1 transponder.
FIG. 2A shows an accommodation method in which a SONET/SDH signal of about 10 Gbps (such as a SONET OC-192/OC-192c signal or an SDH STM-64 signal) is transparently mapped to the OTU3 frame conforming to ITU-T Recommendations G.709. FIG. 2B shows an accommodation method in which a 10 GbE-LANPHY signal is transparently mapped to a frame (described as OTU3′ in FIG. 2), which corresponds to the OTU3 frame conforming to ITU-T Recommendations G.709. In this case, OTU3′, ODU3′, OPU3′, ODTU23′, ODU2′, and OPU2′ shown in FIG. 2B and OTU3, ODU3, OPU3, ODTU23, ODU2, and OPU2 defined in ITU-T Recommendations G.709 are identical in frame structure and different in bit rate, respectively. As is clear from FIGS. 2A and 2B, since the SONET/SDH signal of about 10 Gbps and the 10 GbE-LANPHY signal have different bit rates, it is impossible to accommodate both the signals in a mixed manner and transparently map them to a single 40 Gbps wavelength path (frame).
Accordingly, in the conventional optical network system mentioned above, the nodes A and B use one 40-Gbps wavelength path to transmit three 10 GbE-LANPHY signals (10.3 Gbps) and one SONET OC-192c signal (9.95 Gbps) as a wavelength division multiplexing (WDM) signal having two wavelengths.
As a result, it is inevitable that wavelength resources are wasted and the operation efficiency of a WDM optical network is decreased. Further, since two types of transponders are required, the number of devices provided for each node is increased.
The following are related arts to the present invention.
[Non-Patent document 1] (Related art regarding OTN defined in ITU-T Recommendations)
ITU-T G.709/Y.1331 Interfaces for the Optical Transport Network (OTN)
[Non-Patent document 2] (Related art regarding Generic Framing Procedure (GFP) defined in ITU-T Recommendations G.7041) ITU-T G.7041/Y.1303 Generic framing procedure (GFP)